Outboard motor clutch and interlock



March 31, 1970 s. J. HOFF OUTBOARD MOTOR CLUTCH AND INTERLOCK Filed June 50, 1967 INVENTOR. STEPHEN J. H OFF d4/; *l/Cfu@ AT TO R N EYS United States Patent O U.S. Cl. 11S-18 3 Claims ABSTRACT OF THE DISCLOSURE In an outboard motor, a self-contained clutch assembly of the readily-releasable coil-spring type is mounted immediately below the motor head, as a coupling between the power shaft and the drive shaft, in the enlarged upper end of the exhaust passage through the stern. The clutch is biased to engaged condition and is released by a shift handle operable from front or rear which moves a stop to obstruct rotation of the leading end of the clutch spring. A blocker actuated by the throttle prevents clutch actuation above a selected motor speed.

BACKGROUND OF THE INVENTION This invention relates to an outboard motor having a self-contained clutch between the power head and drive shaft, which is readily installed on a conventional outboard motor with minimum modification.

In conventional outboard motor construction, a power head containing the motor and its controls is mounted at the top of a hollow stem which forms an exhaust passage and houses a drive shaft leading downward and connected by bevel gears in a bottom gear case to the propeller shaft. Various clutches have been embodied in the bottom gear assembly, for lubrication with the gears, but this requires a modified gear assembly and a remote control mechanism. A coil spring clutch in this bottom location is disclosed in Armstrong Patent No. 2,760,613.

SUMMARY OF THE INVENTION In accordance with the present invention, a clutch which requires minimum lubrication and can withstand operation in the exhaust gases is mounted immediately below the power head of the outboard motor, as a coupling between the power shaft of the head and a shorter-thannormal drive shaft. The clutch is preferably a self-contained assembly which is internally biased to engaged condition and releasable by obstructing rotation of a control element. The clutch is desirably a coil-spring type, in which aligned cylindrical driving and driven elements are gripped by a coil spring which tends to wind more tightly on the elements by driving torque and to be released by unwinding action. The clutch is released by obstructing rotation of the leading end of the spring with a simple stop movable into the path of a lug carried with such leading end. Clutch actuation above a selected safe speed is prevented by a blocker member, spring pressed to retracted position and moved into blocking position by advance of the throttle of the power head.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing illustrates the invention. In such drawing:

FIG. 1 is a side elevation of a conventional outboard motor which has been modified to embody the invention, and showing the shift member locked in retracted, clutchengaged position.

FIG. 2 is a fragmental view similar to FIG. l, showing the clutch shift member in the clutchreleasing position; and

3,503,360 Patented Mar. 3l, 1970 FIG. 3 is an axial sectional view of the self-contained clutch assembly used in the embodiment of FIG. l.

DESCRIPTION OF THE PREFERRED EMBODIMENT The outboard motor shown in the drawing comprises a power head containing a motor having a power shaft 12 projecting downward through its lower wall 14. As shown, this is an internally splined shaft which in the 0 conventional motor receives the upper splined end of the standard drive shaft.

The power head has a throttle control member 16 which as shown is mounted for reciprocation, but may be mounted for other movement, such as swinging movement across the front face of the head 10'.

The head 10 is bolted to the top ange of a transfer case 20 carried at the upper end of the hollow stem 22 yby which the motor assembly is supported. The case 20 forms a transfer chamber 24 leading from the exhaust ports of the power head 10 to the exhaust passage in the hollow stem 22. The lower end of the stem 22 is enlarged rearward to convey the exhaust gases toward an exhaust outlet 26, and the stem is joined to a lower assembly 28 which defines a gear case 29 in which the propeller shaft 30 is journalled. A drive shaft 32 extends axially through the stem 22 and into the gear case 29, where it is connected by bevel gears to the propeller shaft 30.

In the outboard motor shown, the propeller shaft is not reversible and reverse drive is obtained 'by rotating the drive assembly in its mounting. To this end, the upper portion of the stem 22 is provided with bearing surfaces 34 and 36 which are supported for rotation through 360 in bearing collars 35 and 37 on a swivel bracket 40; Such bracket is tiltably mounted on a mounting clamp 42 by a transverse pivot bolt 44. For manual control, the power assembly carries a handle bar having a forward portion 46 to which a control handle 48 is pivoted, and a rear portion 49 which forms a carrying handle and provides a grip when the power assembly is rotated lin the supporting bracket 40.

In accordance with the present invention, a self-contained clutch assembly 50 is interposed as a coupling between the power shaft 12 and the upper end of a shortened drive shaft 32. Such assembly 50 is shown in axial section in FIG. 3. It comprises a stub shaft 52 having a splined upper end for reception in the splined opening of the power shaft 12. Such shaft 52 carries a fixed collar 54 which forms the driving element of the clutch, and its lower end forms a spindle for a bearing 56 which rotatably supports a driven collar 58. The driven collar 58 is held onto the spindle portion of the shaft 52 by a washer 59 retained by a screw. The lower end of the driven collar S8 projects beyond the shaft 52 and is threaded onto a drive sleeve 60 which is internally splined to receive the upper end of the drive shaft 32.

The driving collar 54 and the driven collar 58 are formed with aligned cylindrical outer surfaces, and are drivingly interconnected by a coil-spring 62. This is wound of wire of rectangular cross section, and is sized to snugly fit and grip the cylindrical surfaces of the two collars. The spring is wound in a direction such that driving torque causes the coil-spring to wind tighter on the cylindrical surfaces, and hence to grip them and transmit drive from the driving collar S4 to the driven collar 58. Reverse torque tends to unwind the spring and releases the drive connection.

For purposes of releasing the clutch, the upper and leading end of the spring carries an out-tumed tang 64 engaged in a notch in a sleeve 66 which surrounds the spring 62 and which is provided with a radially projecting rib 68. To disengage the clutch, a stop is projected into the path of the rib 68 to obstruct rotation of the sleeve 66 and the tang 64 at the leading end of the spring. Rotation of the driving collar 54 will then tend to unwind the spring 62 with respect to the stationary tang '64, and will release the spring from driving engagement with the driving collar 54. The clutch will be re-engaged by releasing the stop rib 68 for rotation. The spring will then again tighten about the driving collar 54, and the torque will again tighten the grip and clutch the collars together.

The clutch assembly 50 is mounted as a self-contained coupling between the power shaft 12 and the drive shaft 32, and is held coaxial therewith by the fit of the shaft 52 in the shaft 12. The assembly is located in the chamber 24 formed by the transfer case 20. Its embodiment in a conventional outboard motor structure, therefore, requires no modification of that structure save only for the substitution of a shortened drive shaft 32 in place of the conventional drive shaft. The clutch assembly is made of materials to withstand the effect of exhaust gases, such as a suitable stainless steel, and is found to operate satis- Eactorily in the relatively unfavorable environment of this convenient location.

The clutch control mechanism requires a minimum of modification of the conventional outboard motor structure. The control mechanism shown comprises a stop pin 70 mounted for sliding movement through a hole bored in the transfer case 20. The pin is movable to an inward position in which its inner end lies in the path of the stop rib 68 of the clutch assembly 50, as shown in FIG. 2, to obstruct rotation of the sleeve 66 and disengage the :lutch as described above. The pin is also movable to an auter position in which its inner end is withdrawn from ;he stop rib 68 to allow the clutch to engage.

Movement of the stop pin 70 is controlled by a shift Jar 72 which extends forward to a front shift handle 74 ind rearward to a shift handle 76 so that the clutch can be operated in all rotative positions of the power assembly.

Desirably, means is provided to prevent engagement, )r to prevent both engagement and disengagement, of the :lutch when the motor is operating at a speed above a selected safe speed-To this end, the control pin 70` is :onnected to the shift rod 72 by a bracket 78 which in the ihifting operation moves past the position of a blocker ain 80. This is slidably mounted on a bracket 82 for /ertical movement into and out of the path of the bracket 78. The blocker pin 80 is normally ibiased to retracted iosition by a spring 84, and its upper end lies in the path )f a cam 86 mounted on the throttle control member 16. Nhen the throttle control member 16 is in low speed Josition, as shown in FIG. 2, the cam 86 allows the blocker )in 80 to rise out of the path of the bracket 78 and pernits the clutch shift rod 72 to be freely shifted between :lutch engaging and disengagingI positions. With the clutch md its control mechanism in disengaged position, as :hown in FIG. 2, if the throttle control member 16l is noved to the right to high speed position, the cam 86 vill force the stop pin 80 downward into the path of the )racket 78 where it will prevent movement of the clutch hift mechanism 72 from the disengaged position shown n FIG. 2. The clutch can then not be engaged until the hrottle has been returned to low speed position.

Similarly, when the clutch control pin 70 is in retracted, :lutch-engaged position as shown in FIG. l, movement f the throttle member 16 to the right to high speed posiion will force the blocker pin 80 downward behind the )racket 78, where it will prevent the clutch shift mech- .nism 72 from moving to its clutch-disengaging position. This locked-out condition is shown in FIG. 1.

By the simple replacement of the standard drive shaft Vith a shorter drive shaft 32, the insertion of a clutch tssembly 50, and addition of a simple control, a con- 'entional outboard motor having no clutch is provided vith a highly satisfactory and effective clutch; and at mall additional expense such clutch can readily be interocked with the throttle to prevent lutch actuation above l selected safe Speed,

I claim as my invention:

1. An outboard motor having a power head including a power shaft, positioned at the upper end of a stem which forms an exhaust passage and houses a drive-shaft for connecting the power shaft of the head to a propeller at the lower end of the stem, wherein the improvement comprises,

a clutch assembly interposed between the power shaft and the drive shaft at the upper end of the stem, said clutch assembly having relatively rotatable driving and driven parts and clutch means therebetween 'biased to clutched position, a de-clutching element rotatable with the clutch assembly and operable when n stopped to de-clutch the clutching means,

said clutch driving member being releasably inter-fitted with said power shaft and supported thereby in coaxial relation, and said driven member being supported in coaxial relation from said driving member, the clutch assembly being telescopically engaged with said power shaft and held against separation by said drive shaft, whereby said clutch assembly is removable by axially separating the power head and the drive shaft,

a clutch control element mounted on the outboard motor structure for actuation into and out of the path of said de-clutching element to disengage and engage the clutch, and

manually operable means for actuating said control element.

2. An outboard motor having a power head including a power shaft, positioned at the upper end of a stem which forms an exhaust passage and houses a drive-shaft for connecting the power shaft of the head to a propeller at the lower end of the stem, wherein the improvement comprises,

a clutch assembly interposed between the power shaft and the drive shaft at the upper end of the stem, said clutch assembly having relatively rotatable driving and driven parts and clutch means therebetween biased to clutched position, a de-clutching element rotatable with the clutch assembly and operable when stopped to de-clutch the clutching means,

a clutch control element mounted on the outboard motor structure for actuation into and out of the path of said de-clutching element to disengage and engage the clutch, and

manual operable means for actuating said control element,

said stem being mounted in a supporting bracket for 360 rotation, to reverse the drive direction of the m0- tor, and said manually operable means including an extension accessible at the rear of the motor for actuating said control element when the motor is in reversed position.

3. A self-contained clutch assembly for use in an outboard motor having a power head containing a power shaft, the power head being positioned at the upper end of a stem which forms an exhaust passage and houses a drive shaft for connecting the power shaft of the head to a propeller at the lower end of the stern,

said clutch assembly being adapted to be interposed bctween the power shaft and the drive shaft at the upper end of the stem, and said clutch assembly comprislng a clutch driving element including a shaft portion and means formount ing the same in coaxial engagement with the lower end of said power shaft to be driven thereby,

a collar fixed to said shaft portion and having a cylindrical outer surface for engagement by a clutch drive spring,

a clutch driven element including a sleeve mounted for rotation on said driving element coaxial with said shaft portion below said fixed collar and having a cylindrical outer surface aligned with said fixed-collar surface for engagement by the same clutch drive 5 6 spring, means to retain said sleeve against axial disture and movable in response to manual actuation placement from said shaft portion, into and out of the path of said de-clutching eleand a drive sleeve carried by said driven clutch element ment.

sleeve and having a splined element coaxial with and References Cited beyond said shaft portion for axially-separable drive engagement with said drive shaft, and a helical clutch UNITED STATES PATENTS drive spring in engagement with said cylindrical sur- Re 25,229 4/1962 Sacchini et al 192-*26 X faces to clutch the driving and driven elements to- 1824735 9/191 Johnson 11S-18 gether 2,755,897 7/1936 Strang 192-.096 and means to arrest rotation of the leading end of the 10 2,780331 2/1957 Armstrong 192-'07 3,277,986 10/1966 Bear@ 192-26 spring, said last named means comprising a de-clutching element rotatable with the clutch assembly and FERGUS S MIDDLETON, Primary Examiner operable when stopped to disengage the clutch, said de-clutching element being stoppable by a clutch con- U,S. C1. X.R.

trol element mounted on the outboard motor struc- 15 192-.096 

